1. Field of the Invention
The present invention relates to a novel dye mixture, which is improved in solubility and excellent in fastness, and a color composition, particularly, a color composition for image formation, for example, ink, inkjet recording ink or paint, an inkjet recording method and a method for improving ozone gas resistance of a color image material formed.
2. Description of the Related Art
As for image recording materials, materials for forming color images especially predominate in recent years. Specifically, recording materials for inkjet system, recording materials for heat-sensitive transfer system, recording materials for electrophotographic system, silver halide photosensitive materials for transfer system, printing inks, recording pens and the like are actively utilized. Also, color filters are employed in image-sensor; for example, CCD with respect to photographic equipment and in LCD or PDP with respect to display in order to record or reproduce color images.
In the color image recording materials and color filters, dyes or pigments for three primary colors of a so-called additive color mixing process or subtractive color mixing process are used in order to record or reproduce full color images. In the present circumstances, however, a dye that has absorption characteristics capable of achieving preferable color reproduction area and is strong to withstand various use conditions is not available and improvements have been strongly desired.
Inkjet recording methods have been rapidly spread and are still expanding because material cost is inexpensive, high speed recording can be carried out, noise at the recording is low and color recording can be easily conducted.
The inkjet recording methods include a continuous system where a liquid droplet is continuously ejected and an on-demand system where a liquid droplet is ejected corresponding to signal of image information. As for the ejecting system, the inkjet recording methods include a system where a liquid droplet is ejected by applying pressure using a piezoelectric element, a system where a liquid droplet is ejected by generating a bubble in ink with heating, a system where a liquid droplet is ejected utilizing an ultrasonic wave and a system wherein a liquid droplet is ejected by an electrostatic attractive force.
Also, an aqueous ink, an oily ink or a solid (melting type) ink is used as an ink jet recording ink.
It is requested for a dye used in the ink jet recording ink to have good solubility or dispersibility to a solvent, to be capable of recoding in high density, to have good hue, to have good fastnesses to light, heat and active gas (for example, oxidizing gas, e.g., NOx or ozone, or SOx) in environment, to be excellent in fastnesses to water and chemicals, to have a good fixing property to an image-receiving material so as to be hardly blurred, to have good preservability as an ink, to be nonpoisonous, to have high purity, and to be available inexpensively.
Toner ordinarily obtained by dispersing a coloring agent in a resin particle is widely used in color copiers or color laser printers utilizing an electrophotographic process. Performances required to the color toner include absorption characteristics capable of achieving preferable color reproduction area, high transmittance (transparency), which is particularly a problem in the case of using it in an overhead projector (OHP), and various fastnesses under conditions of use environment. Toners obtained by dispersing a pigment as the coloring agent in a particle are described in JP-A-62-157051 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-62-255956 and JP-A-6-118715. Although these toners are excellent in light fastness, they are apt to aggregate due to their insolubility and cause problems of decrease in transparency of a color layer and change in hue of transmitting color. On the other hand, toners using a dye as the coloring agent are described in JP-A-3-276161, JP-A-7-209912 and JP-A-8-123085. However, these toners have a problem in the light fastness though they exhibit high transparency and no hue change.
The heat-sensitive transfer recording has advantages in that an apparatus is small-sized and capable of reducing a cost, in that operation and maintenance are easy and in that a running cost is inexpensive. Performances required to the dye used in the heat-sensitive transfer recording include absorption characteristics capable of achieving preferable color reproduction area, compatibility between heat transferability and fixing property after the transfer, heat stability and various fastnesses of the image obtained. However, dyes hitherto known do not satisfy all of these performances. For instance, a heat-sensitive transfer recording material and an image forming method wherein a chelate is formed between a heat diffusible dye and a transfer metal ion previously incorporated into an image-receiving material for the purpose of increasing the fixing property and light fastness are described in JP-A-60-2398. However, the absorption characteristics of the chelate dye formed are at an unsatisfied level and an environmental problem due to the use of transition metal may occur.
Since high transparency is required to color filter, a method referred to as a dying method of conducting coloration using a dye has been used. For instance, a method wherein a photoresist capable of being dyed is pattern-exposed and developed to form a pattern and the pattern is then dyed with a dye of filter color is repeatedly performed in series with all filter colors to produce a color filter. Other than the dying method, a color filter can be produced by a method of using a positive resist as described in U.S. Pat. No. 4,808,501 and JP-A-6-35182. Although these methods provide high transparency and are excellent in view of optical characteristics of color filter because of using the dye, they have limitations on the light fastness, heat fastness and the like. Thus, a dye excellent in various fastnesses and having high transparency has been desired. On the other hand, a method of using an organic pigment that is excellent in the light fastness and heat fastness in place of the dye is also well known. However, it is hard in the color filter using the pigment to achieve the optical characteristics obtained by using the dye.
It is very difficult to find a dye that satisfies these requirements at a high level. In particular, it is strongly requested for a dye to have a preferable cyan hue and to have good fastnesses to light, humidity and heat, particularly, fastness to oxidizing gas, for example, ozone in environment, in the case of printing on an image-receiving material having an ink-receptive layer containing porous white inorganic pigment particles. Also, it is strongly desired for the dye to satisfy preservation stability of ink described hereinafter.
A cyan dye skeleton for use in the inkjet recording ink includes, for example, a phthalocyanine type, an anthraquinone type and a triphenylmethane type. Although phthalocyanine compounds, which are excellent in hue and light fastness, are ordinarily used, they do not have sufficient fastness to oxidizing gas, particularly ozone and are unsatisfactory in view of ink stability. Therefore, further improvements are requested.
Representative phthalocyanine dyes most widely reported and utilized include phthalocyanine derivatives classified into [1] to [6] shown below.    [1] Copper phthalocyanine type dye, for example, Direct Blue 86 or Direct Blue 87 (for example, a mixture of compounds represented by formula Cu—Pc—(SO3Na)m, wherein m represents 1 to 4). The term “Pc” as used in the above formula represents a phthalocyanine skeleton (hereinafter the same).    [2] Phthalocyanine type dye, for example, Direct Blue 199 and described, for example, in JP-A-62-190273, JP-A-63-28690, JP-A-63-306075, JP-A-63-306076, JP-A-2-131983, JP-A-3-122171, JP-A-3-200883 and JP-A-7-138511 (for example, a mixture of compounds represented by formula Cu—Pc—(SO3Na)m(SO2NH2)n, wherein m+n represents 1 to 4).    [3] Phthalocyanine type dye described, for example, in JP-A-63-210175, JP-A-63-37176, JP-A-63-304071, JP-A-5-171085 and WO 00/08102 (for example, a compound represented by formula Cu—Pc—(CO2H)m(CONR1R2)n, wherein m+n represents a number of 0 to 4).    [4] Phthalocyanine type dye described, for example, in JP-A-59-30874, JP-A-1-126381, JP-A-1-190770, JP-A-6-16982, JP-A-7-82499, JP-A-8-34942, JP-A-8-60053, JP-A-8-113745, JP-A-8-310116, JP-A-10-140063, JP-A-10-298463, JP-A-11-29729, JP-A-11-320921, EP 173,476A2, EP 468,649A1, EP 559309A2, EP 596,383A1, DE 3,411,476, U.S. Pat. No. 6,086,955, WO 99/13009 and British Patent 2,341,868A (for example, a compound represented by formula Cu—Pc—(SO3H)m(SO2NR1R2)n, wherein m+n represents a number of 0 to 4, provided that m is not 0).    [5] Phthalocyanine type dye described, for example, in JP-A-60-208365, JP-A-61-2772, JP-A-6-57653, JP-A-8-60052, JP-A-8-295819, JP-A-10-130517, JP-A-11-72614, JP-T-11-515047 (the term “JP-T” as used herein means a published Japanese translation of a PCT patent application”), JP-T-11-515048, EP 196,901A2, WO 95/29208, WO 98/49239, WO 98/49240, WO 99/50363 and WO 99/67334 (for example, a compound represented by formula Cu—Pc—(SO3H)1(SO2NH2)m(SO2NR1R2)n, wherein 1+m+n represents a number of 0 to 4).
[6] Phthalocyanine type dye described, for example, in JP-A-59-22967, JP-A-61-185576, JP-A-1-95093, JP-A-3-195783, EP 649,881A1, WO 00/08101 and WO 00/08103 (for example, a compound represented by formula Cu—Pc—(SO2NR1R2)n, wherein n represents a number of 1 to 5).
Though phthalocyanine dyes as represented by Direct Blue 87 or Direct Blue 199, which is ordinarily widely used at present, and described in patents described above have a feature excellent in light fastness in comparison with a magenta dye or a yellow dye, they are apt to cause a problem resulting from solubility of the dye. For instance, dissolution defect occurs at the time of production to cause production trouble and insoluble substances are deposited at the time of storage or use of the product to cause a problem often. Particularly, in the inkjet recording described above, because of poor preservation stability of the ink, for example, formation of the deposition of dye, clogging of printing head and ejection defect occur to result in sever deterioration of print image.
Further, the dyes are apt to cause fading upon oxidizing gas, for example, ozone, which recently comes up often on environmental problem, thereby causing a problem in that print density considerably decreases.
The inkjet recording rapidly increases its field of use and is using more and more for home, SOHO and business purposes. As a result of exposure to various use conditions and use circumstances, occurrence of trouble on the preservation stability of ink due to the dissolution defect of cyan dye and a problem on the fading of print image caused by exposure to light or active gas in environment may increase. Therefore, a dye, which has particularly good hue, is excellent in light fastness and fastness to active gas (for example, oxidizing gas, e.g., NOx or ozone, or SOx) in environment, and has high solubility and an ink composition using such a dye have been strongly desired.
Phthalocyanine dyes having ozone gas resistance are hitherto described, for example, in JP-A-3-103484, JP-A-4-39365 and JP-A-2000-303009. However, these dyes do not achieve simultaneous pursuit of hue and fastnesses to light and oxidizing gas at present. In particular, there is no report on property of dye serving as a guideline for the ozone gas resistance. Further, though the use of phthalocyanine is described, for example, in EP 1,243,626A1 and EP 1,243,627A1, the required performance does not reach at satisfactory level. Specifically, the fastness largely depends on density (fastness is improved only in a high density area), and in the high density area, light is reflected due to the occurrence of bronze phenomenon, whereby not only optical density of the recording image decreases but also hue of the recording image largely differs from the desired hue.
Moreover, when azaphthalocyanine compound described in WO 02/34844 is used as a cyan dye in ink, hue of the azaphthalocyanine compound considerably shifts to a shorter wavelength side and as a result, absorption characteristics capable of achieving preferable color reproduction area are not satisfied. Although change of a center metal (for example, Ni) of the metal phthalocyanine compound is somewhat effective for improvement in the hue (shifting to a longer wavelength side), the absorption characteristics capable of achieving preferable color reproduction area are still not at a satisfying level, and a further problem of material safety due to the use of Ni may occur.
An aqueous ink is mainly used as ink for inkjet recording system (hereinafter referred to as an “inkjet recording ink”). The aqueous ink is essentially composed of a dye, water and an organic solvent, and contains water as a main solvent from the standpoint of odor and safety to the human body and ambient surrounding. As the dye, a water-soluble dye, for example, an acid dye, a basic dye, a reactive dye or a direct dye is employed.
With respect to the inkjet recording ink (and dye), the characteristics required include those described below.
Specifically, the characteristics include, for instance, that the ink has appropriate physical properties, for example, viscosity, surface tension, relative conductivity, density and pH, that the ink is excellent in preservation stability for a long period of time, that the ink has high dissolution stability of dissolving components to prevent clogging of nozzle, that the ink is excellent in quick-dry property on an image-receiving material, and that the ink provides a clear recording image excellent in light fastness and water resistance. However, hitherto inks do not satisfy all of these characteristics.
In an aqueous ink conventionally utilized, a water-soluble dye is used. Therefore, the aqueous ink has a large problem in the water resistance and when the recording image is watered, the dye is dissolved out to cause blurring or disappearance of the recording image. Particularly, the clogging of head is also a large problem in the inkjet recording system and various investigations mainly directing to improvement in preservation stability of the ink are made at present.
For instance, ink using a pigment or an oil-soluble dye as the coloring agent and a method of adding, for example, an organic solvent or a resin to an aqueous ink using a water-soluble dye have been investigated. However, the ink using a pigment is poor in dispersion stability and has problems of inferior preservation stability and occurrence of clogging of nozzle. The ink using an oil-soluble dye has problem of environmental health, for example, odor, and a large extent of ink blur to cause degradation of image quality, because the ink contains the organic solvent. Further, the ink containing an additive also has problems of inferior preservation stability, occurrence of clogging of nozzle and inferior ink ejection due to high viscosity of the ink.
Phthalocyanine dyes improved in dispersion stability and having excellent preservation stability are described in JP-A-2000-303014 and JP-A-2000-313837. However, these dyes still do not achieve simultaneous pursuit of hue and fastnesses to light and oxidizing gas and fail to provide a product sufficiently meeting the requirements of the market.
Recently, inks using aqueous dispersion comprising as a dispersoid, a polyester resin colored with a dye or pigment are described, for example, in JP-A-6-340835, JP-A-12-239584 and WO 00/08102. However, these inks still not sufficient to resolve the above-described problems. Further, it is described that with respect to the dye, its compatibility with the resin, which directly relates to decrease in image density, deterioration of water resistance, preservation stability, clogging of nozzle and the like, and control of an average particle size of the colored resin fine particles remain to be solved.
Regarding a phthalocyanine compound (mixture), as described, for example, in WO 00/17275, WO 00/08103, WO 00/08101, WO 98/41853 and JP-A-10-36471, in general, an unsubstituted phthalocyanine compound is sulfonated and an alkali metal salt, for example, a sodium salt, of the sulfonated compound is used as it is as a water-soluble dye. On the other hand, in the case where it is used as an oil-soluble dye, the sulfonated compound is subjected to reactions for sulfonylchloridation and amidation to synthesis the desired dye.
In an aqueous cyan color ink for inkjet heretofore employed, a water-soluble dye, for example, a copper phthalocyanine compound having as a substituent, a sulfo group or a salt of sulfo group prepared by sulfonation of a copper phthalocyanine compound is used.
In such a case, the sulfonation may occur on any position of the phthalocyanine nucleus and further, it is difficult to control a number of the sulfo group introduced. Therefore, when the sulfo group is introduced under such conditions, a position and a number of the sulfo group introduced in the product cannot be specified and a mixture of products different in the number of substituent and the position of substituent is inevitably obtained.
As a result, a component having low solubility, for example, a component having zero or only one sulfo group on the phthalocyanine nucleus exists in the mixture, and when the mixture is used as a water-soluble dye, solubility tends to be insufficient. Therefore, it has been desired to improve the solubility.
On the other hand, as the oil-soluble dye, a phthalocyanine compound having a sulfamoyl group and/or an ammonium salt of a sulfonic acid containing an ion pair between a sulfo group and an amine compound is known. The phthalocyanine compound is produced by conducting chlorosulfonation of a metal phthalocyanine compound with chlorosulfonic acid and then reaction of the resulting chlorosulfonated product of phthalocyanine compound collected with an amine compound (described, for example, in Yutaka Hosoda, Riron Seizo Senryo Kagaku, Fifth Edition, pages 798 to 799, published on Jul. 15, 1968, Gihodo Shuppan Co., Ltd.). According to the production method, in the reaction between the chlorosulfonated product of phthalocyanine compound and the amine compound, the chlorosulfonyl groups are partially hydrolyzed to form a sulfo group in addition to the formation of a sulfonic amido group, or a phthalocyanine compound including an ammonium salt of a sulfonic acid containing an ion pair between a sulfo group and an amine compound is obtained.
When the phthalocyanine compound thus-obtained is used as a dye for inkjet recording, a problem causes in that the solubility thereof in a solvent of the ink is so low that the preparation of ink cannot be carried out or ink having necessary concentration cannot be prepared. In addition, due to the remaining sulfo group, blur occurs when printed on plain paper, water resistance of recording image is poor, and other various characteristics are adversely affected in some cases.
As described above, since various characteristics of the ink for use in the inkjet recording system particularly depend greatly on the inherent characteristics of dye, it is very important to select a dye satisfying the various conditions described above.
In JP-A-2003-34758, a phthalocyanine compound (mixture) having a pyridine ring, a pyrazine ring and a benzene ring is described. However, a phthalocyanine compound in which a substituent and a substitution position are specified and which is further improved in fastness (particularly ozone resistance) has been required.
In JP-A-2004-2670, a dye mixture having fastnesses to light, heat, humidity and active gas in environment is described. However, since the dye mixture has an ionic hydroxy group, it has low solubility in an oily solvent, is poor in dispersibility, causes blur when printed on plain paper, and deteriorates water resistance of recording image. Therefore, further improvements have been required.